    head-principle
    head-first
    {:comment "h21"
-    :schema-symbol 'h21 ;; used by over-each-parent to know where to put children.
-    :first :head}))
+    :schema-symbol 'h21})) ;; used by over-each-parent to know where to put children.
 
 (def h22
   (unify-check

   head-first
   {:comment "h22"
    :schema-symbol 'h22 ;; used by over-each-parent to know where to put children.
    :first :head}))

(def h32
  (unify-check

   head-first
   {:comment "h10"
    :schema-symbol 'h10 ;; used by over-each-parent to know where to put children.
    }))

(def h21
  (unify-check
